Heel construction method for injection molded article of footwear

ABSTRACT

A method of constructing an article of footwear having a molded integrated vamp and sole is described. The method comprises molding the integrated vamp and sole with an external cavity formed in an exterior surface of a heel portion of the integrated vamp and sole. A plug is formed for close fit in the cavity. The plug has inner and outer surfaces and a contour side wall. In one embodiment of assembly, a heat reactive glue is applied to a bottom surface of the cavity and the inner surface of the plug, and at least a portion of the heel portion, having the cavity, and the plug are heated whereby to soften the glue to effect a bond between the bottom surface of the cavity and the inner surface of the plug when the plug is placed in the cavity with the inner surface of the plug facing the bottom surface of the cavity. Pressure is applied across the heel portion and the plug to bond the plug in the cavity. In another embodiment of assembly, the plug is glued in the cavity during assembly by applying a glue which is not heat reactive.

TECHNICAL FIELD

The present invention relates to a method of constructing an article of footwear having a molded integrated vamp and sole and wherein the heel portion thereof is provided with an external cavity to reduce the mass of the heel portion during molding to prevent deformation during mold extraction and wherein a plug is inserted in the cavity in the assembly phase of the article of footwear.

BACKGROUND ART

There are various methods used for assembling articles of footwear and an example thereof is illustrated and described in U.S. Pat. No. 7,096,602. As thereinshown, the article of footwear is comprised of various parts and as can be seen an outsole is molded or vulcanized as a single part and assembled to an upper. Because the outsole is molded solid, when the mold is separated there is deformation in the outsole and particularly about the inner surface thereof due to the fact that the rubber molded material is thick particularly in the heel region thereof. Accordingly, to provide comfort to the wearer, it is necessary to provide a heel cradle over the inner heel portion whereby added support and comfort can be provided. Over this cradle there is disposed a sole membrane and over the sole membrane there is further disposed an insole and a filler whereby the sole portion of the boot is comfortable to the wearer. This construction has many parts and is labour intensive.

U.S. Pat. No. 6,675,497 shows a different type of construction of an article of footwear, herein a waterproof shell which is made by a cement lasting process over a molded sole. Again it can be seen that the molded sole portion has its inner surface covered by both a filler insole support as well as an insole disposed thereover. This is to provide comfortable support over the inner surface of the thick sole which has been molded and subjected to deformation during mold separation.

There is therefore a need to provide a method of constructing an article of footwear having a molded integrated vamp and sole and wherein at least the inner surface thereof is substantially free of deformation in the thick regions of the sole portion and particularly the heel portion thereof.

SUMMARY OF INVENTION

According to the above need, it is a feature of the present invention to provide a method of constructing an article of footwear having a molded integrated vamp and sole which substantially overcomes the above-mentioned disadvantages of the prior art and fulfills the above-mentioned need.

Another feature of the present invention is to provide a method of constructing an article of footwear having a molded integrated vamp and sole and wherein the heel portion of the sole is provided with a cavity in an exterior surface thereof whereby to reduce the mass of the injected material within the heel portion thereof and wherein a plug is further provided to seal the cavity during the assembly process of the article of footwear.

Another feature of the present invention is to provide further cavities in the inner surface of the heel portion of the vamp and sole and also in the inner surface of the plug.

A still further feature of the present invention is to provide an article of footwear manufactured and assembled in accordance with the present invention.

According to the above features, from a broad aspect, the present invention provides a method of constructing an article of footwear having a molded integrated vamp and sole. The method comprises molding the integrated vamp and sole with an external cavity formed in an exterior surface of a heel portion of the integrated vamp and sole. A plug is formed for close fit in the cavity. The plug has inner and outer surfaces and a contour side wall. Glue is applied between the bottom surface of the cavity and the inner surface of the plug and the plug is placed in the cavity with the inner surface of the plug facing the bottom surface of the cavity to bond the plug in the cavity.

According to another broad aspect of the present invention a heat reactive glue is applied to a bottom surface of the cavity and the inner surface of the plug, and heating at least a portion of the heel portion having the cavity and the plug whereby to soften the glue to effect a bond between the bottom surface of the cavity and the inner surface of the plug.

According to a further broad aspect of the present invention there is provided an article of footwear, and preferably a waterproof-type article of footwear, which is constructed in accordance with the above-mentioned method of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a fragmented exploded view showing the molded integrated vamp and sole of the present invention with a cavity formed in the outer surface of the heel portion thereof and a plug adapted to be secured within the cavity during assembly of the article of footwear;

FIG. 2 is a plan view showing the inner surface of the plug having been provided with a heat-reactive glue;

FIG. 3 is a side view of the plug;

FIG. 4 is a fragmented section view showing the plug being inserted into the cavity;

FIG. 5 is a plan view, partly fragmented, showing the inner surface of the heel portion of the molded integrated vamp and sole constructed according to the present invention and particularly illustrating the cavities formed in the rigid smooth heel inner surface;

FIG. 6 is a schematic illustration of the heating chamber with the integrated vamp and sole and the plug of the present invention disposed thereon to activate the heat reactive glue; and

FIG. 7 is a schematic view illustrating how the plug is pressure fitted within the cavity in the heel portion of the molded integrated vamp and sole.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings and more particularly to FIG. 1, there is shown generally at 10 an article of footwear having a molded integrated vamp portion 11 and sole portion 12. The sole portion 12 defines a heel portion 13. As hereinshown the heel portion 13 is provided with a cavity 14 formed in an exterior surface 15 of the heel portion 13. A plug 16 is configured for tight-fit within the cavity 14. It is pointed out that the shape of the cavity 14 and the plug 16 may have different configurations and as hereinshown they are shaped to provide foolproof assembly.

The cavity 14 is provided with a bottom surface 17 and a contour side wall 18. A throughbore 19 may be formed within the bottom surface 14 and extend to an interior surface of the sole portion 12.

As shown in FIGS. 2 and 3, the plug 16 is dimensioned for close fit within the cavity 14 and has an inner surface 20 and an outer surface 21. It also has a contour side wall 22 and as hereinshown this side wall tapers inwardly from the inner surface 20 to the outer surface 21 and only slightly whereby to provide a tight fit when secured within the cavity 14.

As shown in FIGS. 1 and 2, the bottom surface 17 of the cavity 14 may be provided with a heat reactive glue 23 thereover. A similar heat reactive glue 24 may also be applied on the inner surface 20 of the plug 21. Although not shown, this glue could also be applied over the contour side wall 18 of the cavity and the contour side wall 22 of the plug 16. This heat reactive glue is applied when heated to a liquid form and immediately upon cooling it becomes dry and is made reactive by heating the glue to a predetermined temperature. Later on in the assembly process the cavity and the plug are heated to activate the glue to glue the plug in the cavity. However, it is pointed out that the gluing of the parts need not comprise this pre-glue application step, and the gluing can be done in one step during assembly of the plug in the cavity.

As shown in FIGS. 2 and 3, the plug 16 is formed with cavities 25 extending from the inner surface 20 into the body of the plug whereby to reduce the mass of injected material required to make the plug. In order to retain a certain amount of rigidity, these cavities 25 occupy less than 50% of the inner surface area 20 of the plug whereby to retain sufficient inner surface area to assure a rigid bond and waterproofing between the plug and the heel cavity 14. The cavities 25 can have any suitable cross-sectional shape.

As shown in FIG. 5, further cavities 26 are also formed in the rigid smooth heel inner surface 27 of the heel portion 13 of the molded integrated vamp and sole. Some of these cavities, namely cavities 26′ are more shallow than the other cavities depending on the amount of rubber material in that region of the heel portion. FIG. 4 illustrates the position and depth of these cavities which are made during the molding stage of the integrated vamp and sole whereby to reduce the mass of material in the heel portion 13 thereof. Again, these cavities can have any suitable cross-sectional shape.

It is pointed out that the purpose of the cavity 14 and the cavities 26 and 26′ is paramount in the molding process of the integrated vamp and sole. The molding thereof is effected by a dye, but obvious to a person skilled in the art, having at least two movable parts and by providing these cavities in the heel portion it is possible to reduce the mass of injected material therein. This reduced mass reduces the weight of the vamp and sole. It also prevents the rigid smooth inner surface 27 in the heel portion 13 of the integrated vamp and sole from deforming when the dye parts are separated after molding with the molding material still hot whereby to maintain this smooth heel inner surface free of deformation to eliminate the need to have a further insole disposed over the heel inner surface or heel cradles as previously described with respect to prior art constructions.

After the molded integrated vamp and sole and the plug have been molded and the heat reactive glue applied thereto and dried, the vamp and sole can then be transferred or shipped to an assembly plant where the article of footwear is completed. However, in the assembly of the article of footwear it is necessary to secure the plug 16 within the cavity 14 and this is done by providing a heating device to reactive the glue, such as the device 30 illustrated in FIG. 6 which is comprised essentially of a bench having a heating chamber 31 provided with resistive heating elements 32 which are controlled by a control device 33 whereby to set the temperature of the heat 34 released therefrom at the open top end 35 of the chamber. In this particular application the heat reactive glue is set to re-activate at a temperature of about 100° F. whereby to cause the glue to soften and provide adequate bonding. The open top end 35 is provided with a support metal screen 36 whereby to provide the escape of heat as herein illustrated at 34′ from the upper surface. The plug 16 and the integrated vamp and sole 12 are disposed over the grate 36 with the heel portion 13 positioned above the heating elements 32 as well as the plug 16 whereby to re-activate the heat reactive glue 23 and 24 in the cavity bottom wall and the inner surface 20 of the plug, respectively. Thereafter the integrated vamp and sole article of footwear 10 is inverted onto a support arm 40 of a press 41, as illustrated in FIG. 7. As hereinshown the heel portion 13 of the integrated vamp and sole is disposed on the support plate 42 at the top end of the support arm 40 and the plug 16 is placed into the cavity 14 as illustrated in FIG. 4 with the heated glue of the plug facing the heated glue over the bottom wall of the cavity 14. The piston 43 is then activated whereby the piston rod 44 will extend and the piston head 45 will press the plug 16 firmly within the cavity 14.

As previously described a through bore 19 may be formed in the heel portion 13 whereby to evacuate air that may be trapped in the cavity as the plug descends within the cavity. Air will escape out of this through bore 19 as indicated by arrow 46 whereby to provide a solid bond between the inner surface 20 of the plug and the bottom surface 17 of the cavity with the glue 23 and 24 bonding together. If glue is applied to the contour side wall 18 of the cavity and the contour side wall 22 of the plug, such will provide an even greater bond and waterproofing between the plug and the cavity. The tapered side walls 22 of the plug also provide for a tight friction fit between the plug and the cavity.

It is pointed out that the molded integrated vamp and sole may be assembled with an upper 50, as illustrated in FIG. 7 prior to the securement of the plug 16 in the heel cavity 14 or this can be done thereafter. It is preferable to do it after because a single inner sole needs to be positioned over the inner surface of the sole portion 12 and as previously described no other inner sole support needs to be secured thereover in view of the fact that there is a smooth inner surface in the heel portion by the method of fabricating the integrated vamp and sole with the heel cavity. Another advantage of the plug 16 is that it can provide an article of decoration or publicity for the article of footwear. For example, the plug 16 can be injected molded with a material of contrasting color from the integrated vamp and sole portion of the article of footwear. Further, the plug can be provided with a decorative logo such as illustrated at 51 in FIG. 1 wherein the trade name of the article of footwear can be molded while providing a traction or gripping surface for the heel region. A further advantage of the plug is that the central portion 52 thereof could also be formed as a further plug to provide a different shock absorbing material depending on the intended use of the article of footwear being fabricated or to provide further customization.

It is further pointed out that by molding the integrated vamp and sole and the plug at a molding plant, the assembly of the article of footwear can be carried out at a remote assembly plant or by the supplier whereby to ensure quality control in the assembly of the article of footwear. This is important, particularly seeing that the process of injection molding and/or galvanizing is effected in a plant which is usually unsuitable for finishing an article of footwear which requires a clean environment for assembly and inspection to ensure quality control.

The invention also envisages the article of footwear constructed in accordance with the method of its construction as described herein and as defined by the appended claims. 

I claim:
 1. A method of constructing an article of footwear having a molded integrated vamp and sole, said method comprising the steps of: i) molding said integrated vamp and sole with an external cavity formed in an exterior surface of a heel portion of said integrated vamp and sole, ii) forming a plug for close fit in said cavity, said plug having an inner and outer surface and a contour side wall, iii) gluing said plug in said cavity with said inner surface of said plug facing said bottom surface of said cavity to bond said plug in said cavity.
 2. A method as claimed in claim 1 wherein said step (iii) comprises the further steps of: (a) applying a heat reactive glue to a bottom surface of said cavity and said inner surface of said plug, and (b) heating at least a portion of said heel portion having said cavity and said plug whereby to soften said glue to effect a bond between said bottom surface of said cavity and said inner surface of said plug.
 3. A method as claimed in claim 2 wherein after step (iii) there is provided the further step of applying pressure across said heel portion and said plug to effect a secure bond between said plug and said cavity.
 4. A method as claimed in claim 1 wherein said step (i) further comprises forming spaced-apart cavities in a rigid smooth heel inner surface of said heel portion to reduce the mass of injected material in said heel portion while retaining said rigid smooth inner flat surface.
 5. A method as claimed in claim 2 wherein said step (ii) further comprises forming cavities in said inner surface of said plug in a surface area of less than 50% to reduce the mass of injected material in said plug while retaining sufficient inner surface area to assure said bond between said plug and said cavity.
 6. A method as claimed in claim 3 wherein said step (ii) further comprises forming a through bore in said heel portion between said bottom surface of said cavity and a rigid inner flat surface of said heel portion to reduce the weight of injected material in said heel portion and to permit evacuation of compressed air when said plug is inserted in said cavity and press-fitted therein.
 7. A method as claimed in claim 3 wherein said step (b) comprises providing a heating chamber having an open-top end with a support screen thereacross for the passage of heat therethrough, placing said integrated vamp and sole and plug on said support screen to soften said heat reactive glue for a predetermined time period, and removing said integrated vamp and sole and said plug therefrom to effect said bonding of said plug in said cavity.
 8. A method as claimed in claim 7 wherein said heating chamber is provided with temperature controllable heating elements, said heating elements having temperature control means which are adjusted for said heating chamber to generate heat at a temperature of about 100° F.
 9. A method as claimed in claim 1 wherein said step (ii) comprises forming said plug with a contrasting color material.
 10. A method as claimed in claim 1 wherein said step (ii) comprises forming said plug with said outer surface thereof having a traction design or logo molded therein.
 11. A method as claimed in claim 1 wherein said plug is formed with said contour side wall tapering outwardly from said inner surface thereof to said outer surface wherein said plug is bonded in friction-fit within said cavity.
 12. A method as claimed in claim 1 wherein said step (iii) further comprises applying glue to said contour side wall of said plug and peripheral side walls of said cavity.
 13. A method as claimed in claim 1 wherein after said step (iii) there is further provided the steps of securing an upper to said integrated vamp and sole, and positioning a single insole over an inner surface of said integrated vamp and sole and extending over said rigid smooth inner surface of said heel portion.
 14. A method as claimed in claim 2 wherein said steps (i), (ii) and (a) are carried out at a molding plant and said step (b) is carried out at a remote assembly plant to ensure quality control in the assembly of said article of footwear.
 15. A method as claimed in claim 13 wherein said upper is secured to said integrated vamp and sole prior to effecting said steps (b) and (iii) and wherein said single insole inserted thereafter.
 16. A method as claimed in claim 5 wherein said step of forming cavities in said rigid smooth heel inner surface of said heel portion comprises forming cavities in less than 50% of said rigid smooth inner surface.
 17. A method as claimed in claim 4 wherein step (i) comprises molding said integrated vamp and sole in a dye having at least two parts, said cavities in said heel portion having reduced the mass of injected material therein preventing said rigid smooth inner surface from deforming when said dye parts are separated after molding whereby to maintain said smooth heel inner surface free of deformation to eliminate the need to have a further insole over said heel inner surface.
 18. An article of footwear constructed in accordance with claim 1 and containing an upper secured to said integrated vamp and sole, and a single insole disposed over said heel inner surface.
 19. A waterproof article of footwear constructed in accordance with claim 1 and containing an upper secured to said integrated vamp and sole, and a single insole disposed over said heel inner surface. 